1. Field of the Invention
This invention relates to a dielectric ceramic composition for use in making microwave devices, and more particularly to a microwave dielectric ceramic composition which exhibits a high dielectric constant .epsilon..sub.r and a high no load Q value, and, in addition, a positive or negative temperature coefficient .eta..sub.f of about zero can be obtained by changing the ceramic composition.
2. Prior Art
Ceramic capacitors utilized for temperature compensation, as well as dielectric resonators for use in microwave circuits or the like have been required to have a high specific dielectric constant .epsilon..sub.r as well as a large no load value Q and further should obtain a positive or negative temperature coefficient .eta..sub.f of the resonance frequency of about zero in consideration of the temperature coefficient of metal to be used in conjunction with the dielectric ceramic composition.
As such a dielectric ceramic composition, a BaO-TiO.sub.2 type, a MgO-TiO.sub.2 -CaO type, and a ZrO.sub.2 -SnO.sub.2 -TiO.sub.2 type composition and the like have heretofore been employed. However, when a dielectric resonator or a capacitor is fabricated with these ceramic compositions, their specific dielectric constant .epsilon..sub.r becomes a low value in the order of 20-40 in the vicinity where its temperature coefficient .eta..sub.f is zero (ppm/.degree.C.). Consequently, the size of such an oversized construction of apparatuses as dielectric resonators and the like fabricated with these materials become too large.